1. Field of the Invention
The present invention relates to a method for detecting and/or removing errors in the transmission and storage of data in a digital/digitally programmable hearing device, and to a hearing device operating in accordance with the method.
2. Description of the Prior Art
European Application 0 341 903 teaches a method for programming a hearing device in which in the data transmission data are programmed into a hearing device from a host computer via an interface, with a check of the data transmitted by the host computer taking place in the interface.
An error check of the data transmitted to the hearing device from the interface does not occur, however.
An object of the present invention is to provide a method and a digital hearing device which enables a detection and/or removal of any errors arising in connection with a hearing aid in the transmission and storage of data.
The above object is achieved in accordance with the present invention in a method and a digital hearing device wherein an internal check of the transmitted and stored data takes place within the hearing device itself.
The inventive method enables the detection of data errors which arise within the hearing device during the course of storage and/or data transmission procedures. Data errors which arise in the hearing aid subsequent to a correct data transmission (possibly from a host computer via an interface) can thus be detected.
Substantially continuous data storage procedures (routines) and data transmission procedures (routines) occur during the operation of a digital/digitally programmable hearing device. Data errors which may occur arising therein are detected by the internal check of the inventive method inside the hearing aid.
In particular, data errors arising in the data transmission between a secondary memory and the main memory are detected by the inventive method. In the operation of a digital hearing device new programs are continuously loaded from a secondary memory into the main memory or from the main memory into the processing unit, so that data errors also can arise in such transmissions with a relatively high probability.
In a further variation the inventive method enables the monitoring of the stability of the data stored in the main memory and/or a secondary memory as well as the detection of undesirable alterations of the stored data.
Data, or data words, stored in the registers of the processor can also be monitored for data stability through the inventive method.
The inventive method further enables an accuracy check to be conducted for data entered by the user(whether by keystroke or programming).
The checking of transmitted and stored data preferably occurs in definable and particularly periodic intervals, so that a high level of data security can be thereby achieved with a justifiable computing outlay.
In an embodiment of the method the frequency of the checking of the transmitted and stored data is determined by the type of data. By means of an integrated decision program it can be determined the priority that the individual data have (e.g. with respect to the comfort or the security for the user) in order to make more frequent checks for data transmission procedures or storage procedures involving data accorded a particularly high priority. A concentration on particularly significant data thus can occur, such data consequently being checked with increased frequency.
By undertaking a data check in the startup/changeover of the hearing aid, the particularly sensitive conditions of the reloading of programs and the initialization (start-up) of the hearing device can be checked, these being particularly susceptible to data errors.
The inventive method offers a particular advantage in the checking of data in connection with a hearing device which functions with an internal digital signal processor (DSP).
In such DSP hearing devices a completely new output signal is generated without direct reliance on the input signal, by means of the received and loaded programs.. The received input signal is analyzed in the DSP and a new output signal is generated via computing processes and programs to be loaded.
Data errors which arise therein can cause discomfort or even hearing damage to the patient due to the generation of an erroneous output signal.
The inventive method enables the avoidance of such miscalculations of the output signal arising in the generation of the output signal due to data errors in the transmission and storage of data.
To check the transmitted and stored data in the context of the inventive method, a parity check can be employed, and it can be determined on the basis of the status of the parity bit whether a data error is present.
In a more expensive form of data checking in the context of the invention, checksums are formed, which allow a greater number of data errors to be detected in comparison to a pure parity check.
Another alternative in the context of the inventive method is to undertake a data check according to a Hamming code technique. This enables a detection and localization of individual data errors so that a focussed removal of the data errors can take place.
After a data error has been detected the erroneous bit can be changed into its correct status again by reversing its logic level. The data error is thereby removed, and there can be further processing within the hearing device with the corrected data record.
For security an automatic shutoff of the hearing device can occur upon the detection of a data error. Dependent on the classification of the checked data (e.g. according to comfort or security aspects, as previously described), upon the occurrence of a data error a response can be made according to the priority of the checked data, such as reversal of the erroneous bit, producing an optical/acoustical display (to allow for manual intervention) or an automatic shutoff of the hearing device.
Particularly in digital hearing devices with a digital signal processor it is advantageous to cause a restart of the program execution given detection of a data error, whereby on the basis of the newly occurring loading of the program (e.g. from the secondary memory into the main memory) there is a renewed data transmission with the possibility of avoidance of the data error.
The inventive digital hearing device can detect arising data errors by means of an integrated checking element for making an internal check of transmitted and stored data inside the hearing device.
For conducting a static parity check, one or more parity decoders can be utilized as such a checking element. Individual data words are entered into such a parity decoder wherein the words are checked for data accuracy by the status of the parity bit.
The checking element of the digital hearing device can alternatively be a checksum unit for generating a checksum from the data record (and comparison with the correct sum). A more costly, but also more precise detection of data errors compared to the parity decoder can then occur by supplying the result to an executive control unit in connection to the checksum unit.
In another embodiment the checking element employs the Hamming code method, which enables a precise localization of individual data errors and thus a simple removal of these errors.
In another embodiment the inventive digital hearing device contains a number of checking elements working according to different principles (e.g. a parity check decoder and a checksum unit and unit according to the Hamming code method) in order to be able to execute data error detection with precision commensurate with the type (priority) of the data being checked.
Since the checking element is connected with the program memory and/or with the processor of the digital hearing device, data errors arising in connection with these components of the digital hearing device can also be detected.
In another embodiment the checking element is connected with at least one operating key and/or with an interface terminal. Data introduced into the digital hearing device via interfaces thus can be checked for accuracy as well. In the transmission of data proceeding from a host computer via an interface a data security check initiated in an interface can be canceled and taken over by the checking element integrated in the digital hearing device.